File photo shows "Su" from Myanmar, who was 17 when she was trafficked to Yunnan, China, in 2007. She was forced into marriage with a Chinese man and had two children before she escaped in 2012.

BEIJING - Chinese authorities in the northern region of Inner Mongolia arrested 31 people on suspicion of trafficking women because they had held 14 people, 11 of them from Myanmar, state media said on Monday.

Five of the non-Chinese victims were younger than 18 and were handed to Myanmar police after a three-month investigation into the gang, which ensnared the women by offering them tours and jobs, the official Xinhua news agency said.

The victims were then sold as wives in rural China for as little as 50,000 yuan ($8,142)

China's gender imbalance, the result of its one-child policy and illicit abortion of girl babies because of a traditional preference for boys, has led to a huge surplus of single men. The latest census showed 118 newborn males for every 100 females.

In September, state media reported that Chinese police would clamp down on websites that sell group tours to enable men to meet "foreign brides" in Southeast Asian countries, as the practice leads to human trafficking and prostitution.

Last year, a US State Department report cited Russia and China as being among the world's worst offenders in fighting forced labour and sex trafficking.